In the movies it goes something like this: The guy won’t talk, so he’s tied to an uncomfortable metal chair. A desk lamp is thrust into his face. And a needle chock-full of truth serum is plunged into his tricep.

Presto. The guy talks.

In real life, though, it goes more like this: The guy is just standing there when a pregnant woman enters his peripheral vision. His brain disconnects, all sense of decorum is thrown out the window and a carnal sense of idiocy reigns.

Presto. The guy — or in plenty of cases, the girl — talks.

And it’s nothing the pregnant woman wants to hear.

As anyone who’s ever been pregnant knows, something strange happens when a woman is with child: She becomes public property.

“I was asked several times if I was having twins as well as asked when I was due with the implication being that it must be any day now,” says Danielle Gilbert, of Alameda. “Most of the comments I got were from Trader Joe’s cashiers trying to be friendly. Why they think it’s friendly to imply I’m a big cow, I don’t know.”

Whether it be unsolicited belly pats or equally unsolicited comments on their size, appearance, or timing between children, pregnant women hear it all.

And don’t stop reading this story in favor of the sports section, nonpregnant people. Because this is all a bunch of preaching to the choir to the pregnants. It’s the nonpregnants who could really stand to learn a lesson in civility. After all, that’s why TheNestBaby.com recently polled its members to unearth the worst pregnancy etiquette faux pas ever committed. The Web site, which launched last June as an offshoot of TheKnot.com and TheNest.com, released its results a few weeks ago.

“We thought it was a good idea to get people educated so they wouldn’t offend their pregnant friends,” says TheNestBaby.com editor in chief Carley Roney. “People don’t realize that a lot of what they say is offensive. They don’t understand how pregnant you are. They don’t understand that you feel as big as a house. And they really don’t understand that you’ve felt as big as a house since you were just eight weeks pregnant, when you couldn’t say anything about even being pregnant to anyone.”

According to TheNestBaby’s extensive, though wholly unscientific, research, there are five top pregnancy etiquette faux pas. The first they call the “Let me touch your belly!” faux pas.

“Across the board, this was the No. 1 offender,” says Roney. “The fact that a pregnant person’s belly is public property is just amazing. One woman told us that at the grocery store, a cashier reached out and rubbed her belly and said it was for her good luck. HER good luck! Not the pregnant woman’s!

The belly pat, truth be told, is a bit controversial. Many belly patters and pattees claim there’s a cultural element to the properly placed pat. In Latino cultures, they say, it is especially common for the pregnant woman’s belly to become a free-for-all, all in the name of well-wishing.

Roney, a mother of two, doesn’t buy it.

“There’s a bit of a culture clash, for sure,” she says, acknowledging she has learned a lot about customs in her marriage to a man of Chinese descent. “And maybe our senses of personal space, over time, will fade away. But I think that even if a woman herself is Latina, there’s a sense that in this generation, and growing up in America, there’s a sense of not wanting people to reach into your own space when you’re so uncomfortable.”

Rounding out the top 5 in TheNestBaby’s poll are labor horror stories (“I tore like you wouldn’t believe!”), assessments of the woman’s size, snide comments on the name chosen for the impending arrival (“Lacey? That sounds like a hooker’s name!”) and encouragement to drink alcohol (“Come on, one drink won’t hurt”).

And lest you think TheNestBaby exaggerates to draw more Web visitors, real, live, formerly and presently pregnant women back up these stories and add their own.

Rita Gaber tells of a trip just last month to the North Berkeley farmers market. She’d taken her two boys, who are 20 months apart, in a double stroller and was included in a conversation between a vendor and a middle-aged man who was waxing poetic about what a joy, and never a challenge, it was to watch his two boys, who were eight years apart, grow up.

Finished self-congratulating himself, the man turned to Gaber and sized up her 3-year-old and 19-month-old.

“I guess you didn’t understand junior high biology, did you?” he said.

“Meaning that I didn’t understand how I got pregnant so quickly the second time around,” fumes Gaber. “To which I replied, ‘Actually, I understood junior high biology very well.’ And it’s true. We had planned to have our kids close together given that we got a late start on family formation. Would he have said something so condescending to my husband? I doubt it.”

But don’t think only men are offenders when it comes to pregnancy etiquette. Women are some of the worst. Especially when it comes to comments about size. And it’s not just comments that a woman looks big, a particular specialty, note local moms, of mothers-in-law. It’s also comments about not being big enough.

Face it, when talking about a woman’s size — whether large or small — it’s a lose-lose proposition — pregnant or not.

Just consider a story told by a colleague at this newspaper. Early on, people said she was so small, she didn’t look pregnant.

“I was on a master’s swim team at the time, and was about four months pregnant. One woman who said she couldn’t tell I was pregnant at all actually went under the water to scope out my belly,” she says. “It was really annoying because it was my first baby, and I was really excited about officially being seen as pregnant.”

And later in her pregnancy? A co-worker exclaimed that he couldn’t believe how huge she was.

Bellies aren’t the only target of comments.

“Did your face look like that before you were pregnant?” was a comment directed toward Pleasanton’s Jennie Geisler when she was pregnant. And Elena Gardella was walking on Telegraph in Berkeley when a guy looked at her and said with disgust, “Oh. You’re bringing another life into the world.”

Even due dates don’t get a reprieve.

“In an elevator at work, a woman asked me when my baby was due,” says Hannah Shafsky, who works at a law firm in Danville. “I told her August. She looked at me in horror and told me my child would endure a terrible childhood as a result of having a summer birthday. I told her it was too late for me to do anything about it.”

Cindy Gunderson, seven months pregnant, thinks the rude questions and comments can be linked to one of three reasons: The people have never had kids and don’t know how to act around pregnant women; they actually have kids but think their experience is far more important than anyone else’s; or they simply notice a pregnant woman and feel the need to say something, anything.

“We have to realize that while pregnancy is a very personal thing, it’s also a very obvious thing, and we just have to laugh,” says Gunderson.

That’s the advice of TheNestBaby’s Roney.

“It doesn’t make any sense to get offended by any of these things,” says Roney. “Like the argument that people wouldn’t make the size or the twins comment to someone who’s just fat. Well, everyone does want to say to the fat person, ‘Wow, what happened? You got fat.’ With pregnancy, it’s truly shocking how big a person gets, and there’s just this huge open door. … There’s a truth serum people take when they see a pregnant person.”